Computer networks are a ubiquitous feature in contemporary computing environments. In many data centers, computer systems within a data center are connected to each other via an internal computer network. The internal computer network is often connected to one or more external networks via one or more routers. Some of the external networks, such as the Internet, may not be under the control of the owner of the data center. Therefore, when a computer system within the internal network connects to an external computer system on an external network, it is important to limit the information revealed to the external computer system. In addition to limiting the data explicitly transmitted from within the internal computer network to the external computer network is important, it is also important to control network metadata transmitted from within the internal computer network to systems on the external computer network.